Peatlands and Climate Change: Survival of the Deepest

Northern peatlands provide important ecosystem services and while these ecosystems are facing large increases in the frequency and severity of climate-mediated disturbances (e.g., wildfire, drought), they are generally resilient to these disturbances. Numerous autogenic feedbacks operate within peatlands that regulate their response to changes in seasonal water deficit. However, our recent research has determined that shallow peatlands have greater water table variability and drawdown rates, moisture stress and depths of burn than deeper peatlands. Moreover, we found that peatland carbon sequestration was significantly lower during periods when the water table became hydrologically disconnected from near-surface peat, which occurs more often in shallow peatlands. This suggests that shallow peatlands are less resilient to disturbance due to the limited capacity of their autogenic ecohydrological feedback mechanisms to mitigate disturbance, when compared to deeper peatlands.We explore how several autogenic feedbacks change in sign and strength with increasing peatland depth and argue that shallow peatlands represent sentinels for climate change; acting as a bellwether for deeper peatlands in a future with more frequent, prolonged, and intense water deficits. We suggest that an explicit quantification of peatland feedback mechanisms across a gradient of hydroclimatic settings, and the thresholds and constraints they operate under, will help identify systems at greatest risk for loss of function or catastrophic degradation under climate change. Furthermore, this work provides insight into peatland restoration and peatland evolution as all deep peatlands were, at one point, shallow and perhaps at the height of their vulnerability.